One nasty problem with CAVEs and augmented reality is, after you try it for a few minutes - stop me if you've heard this one - you throw up. Simulation sickness is caused by lag in the onscreen visuals in response to your head movements. Even delays measured in milliseconds can make sensitive users queasy. They never talk about that on the Star Trek holodeck.
Volume, Volume, Volume
You've already noticed all these methods still use bogus 2-D flatscreen fakery. For genuine three-dimensional graphics out in real space, you're talking volumetric displays. As the remarkably good Wikipedia article notes, the chief problem with volume of the "Help me, Obi-Wan Kenobi" kind is the mind-boggling amounts of data it requires: "For example, a 24-bit 70 volume/sec 1024×1024×768 display might need up to 180 GB/s transferred to the electro-optic modulator components."
Volumetric engineering has made slow, incremental progress, but it's been acceptably steady. Actuality Systems already markets a pricey industrial 3-D display. "Perspecta provides hologram-like spatial 3-D full-color and full-motion images that occupy a volume in space. Users experience an all-encompassing 360-degree view and simultaneous multi-view collaboration without goggles or any assistive device." Actuality targets medical markets, though an October 2006 interview with Actuality founder Gregg Favalora tantalizingly mentions "exciting, hologram-like displays for the desktop and arcade."
San Francisco-based IO2 Technology sells a "floating free-space interactive display," the M2 Heliodisplay. It's a high-tech fog generator that projects an image onto a cloud of micro-droplets. So far, it generates only a 2-D image. Inventor Chad Dyner said in an interview, "You can play games on the Heliodisplay, but the picture quality would work for only certain types of games today." He added, optimistically, "This is not to say that with a future version this would not be more widely adopted."
Research continues. In late November 2006, Japan's National Institute of Information and Communications Technology (NICT) and Kobe University demonstrated a thin-panel device that forms 3-D images in the air.
What do all the companies and institutions cited here share in common? That's right - no gaming connection whatever. For volumetric gaming, you can't find anything beyond a few oddball art projects, like the Matrixx 3-D display built in April 2006 by electrical engineering students at the Delft (Netherlands) University of Technology. What was the Matrixx? In this case, it was a giant array of 8,000 red diodes in 8,000 suspended ping-pong balls connected with four kilometers of copper wire. This grandiose thingy, the largest electronic 3-D display in the history of the world, let passersby play - woohoo, hold me back! - 3-D Snake, Duck Hunt and Pong. That, friends, is the state of the art in true 3-D gaming. Oh well, at least it'll get here faster than your robot housekeeper and your personal helicopter.